Republican state Senator Russell Pearce, a long-time fixture in Arizona politics but until recently a virtual unknown elsewhere, never expected to singlehandedly shake up national politics, let alone get under the skin of the White House.
"Nobody could have guessed the impact it would have," Mr. Pearce said of the divisive law he crafted to crack down on illegal immigrants in his state - of which there are nearly half a million. "Who could have guessed that I would have pissed off the president of the United States?"
A 63-year-old father of five and former lawman who worked for the local Maricopa County Sheriff's Office for 23 years, Pearce is clearly reveling in the political shockwaves he has created. He says he is also pleased to have called attention to what he and many other Americans consider misguidedly lenient policies toward illegal immigrants.
As a result, Arizona - the desert state that provided presidential candidates in Barry Goldwater and John McCain - has become a crucible for policy on immigration, an issue that crystallizes popular anger ahead of the midterm congressional vote in November.
The state's controversial law goes into effect Thursday, barring successful legal challenges. It will make it a crime to be in the country without proper documents. Local backers say the legislation's intent is to curb the smuggling of both humans and drugs over the state's porous border with Mexico.
It also requires state and local police officers to check the immigration status of anyone they suspect is unlawfully in the country, even during routine traffic stops. Critics say that this will inevitably result in widespread harassment of Hispanic or Hispanic-looking Americans.
Even so, polls show the Arizona approach is supported by a solid majority of Americans - a Rasmussen Reports poll in late May found 55 per cent of respondents nationally would like a similar law in their own state. Consequently, some political experts say President Barack Obama's steadfast opposition to it will likely help galvanize grass-roots Republican groups.
More significantly, the new law appears to be inspiring copycat efforts in at least 20 other states. That is in addition to the five states that have already introduced similar legislation this year.
As wedge issues go, however, this one may well end up languishing in the desert. Many political analysts say illegal immigration is unlikely to be a deciding factor in all but a handful of contests - mostly in Arizona itself.
And the eventual backlash against the measure, experts say, could prove severe for its champions, alienating an increasingly affluent Hispanic electorate once considered a potential conservative goldmine for the Republican Party.
Mr. Pearce has been working for years on state measures to curb illegal immigrants. An earlier law he championed that ultimately passed required employers to verify their workers using a federal computer system dubbed "E-Verify." That one was passed in 2007.
With conservative allies in the state legislature - where Republicans control both the House and Senate - he crafted the law with input from the Federation for American Immigration Reform, an organization that pushes for restrictions on immigration and has supported a raft of state and city ordinances across the country.
As the legislation took shape this year, Mr. Pearce got together with then-Maricopa County Attorney Andrew Thomas and consulted University of Missouri-Kansas City School of Law professor Kris Kobach. In the words of Kobach, the two sought to make the bill, known as SB 1070, a "bullet-proof law that would withstand any and all changes." They knew the legal challenges were coming.
The bill also needed the political stars to align to become law, and in a strange twist, Mr. Obama himself made it possible. Before she went to Washington in January of last year as Mr. Obama's Homeland Security secretary, Arizona's former Democratic Governor Janet Napolitano was quick to veto many of the Republican-dominated Arizona legislature's proposals, setting a state record for vetoes with 180 proposals tossed out over seven years in office.